Granite Crushing Screenings as a Component Factor in the Concrete Structure Formation. Part II: Experimental Studies of Structure-forming Potential

Abstract

The paper considers the results of experimental studies of the individual and joint influence of macro-, meso- and micro-nanofractions of granite crushing screenings on the processes of structure formation and properties of cement concrete. It has been established that in the processes of formation of the structure of fine-grained concrete and the potential for resistance to its destruction, all fractions of stone crushing screenings perform their specific functions as a component factor. Macro-sized (crushed stone) grains of screening of the 5–10 mm fraction form a macro-scale frame of the addition system, which perceives force load with the accumulation of loading energy and braking of main cracks. Sand mesoparticles of fraction 0.16–5 mm fill the intergranular space of the system for adding macroparticles with dissipation of external loading energy in the matrix material. The microfraction of granite crushing screenings (the fraction is <0.16 mm), along with the effect of replacing the volume of cement stone, exhibits physical and chemical activity in the phase formation of hydrate compounds. It is shown that in the initial screening of granite crushing, the structure-forming role of its particles is not manifested effectively enough, the main reason for which is the “excess” of sand fractions, which push apart the grains of macrofractions and increase the water demand of the concrete mixture. Traditional methods of enriching screenings do not solve this problem. The principle of conditioning screenings by saturating them with macro- and micro-sized fractions is discussed. Based on this principle, a technology for mechanical processing of screenings has been developed to produce a “line” of products for targeted use in the building materials and products industry. The introduction of such technology will significantly increase the efficiency of construction and technological recycling of stone crushing screenings through maximum use of the structure-forming potential of their polydisperse composition.